The present invention is directed to a valve with a backflow preventer to prevent liquid backflow from the valve outlet to the valve inlet.
In some types of valves, it is desirable to provide means for preventing liquid backflow through the valve. One example of such a valve is one that is connected between a source of fresh water and a device for utilizing the water which may contaminate the water as it passes through the device. To prevent contamination of the source of fresh water due to backflow, a backflow preventer may be incorporated in the valve to prevent liquid from flowing from the valve outlet to the valve inlet.
One example of a valve with a backflow preventer is disclosed in U.S. Pat. No. 3,424,184 to Brimley, et al. That valve incorporates a backflow preventer in the form of a movable ball which may seat on a pair of spaced-apart O-rings provided in the main flow channel of the valve. In normal operation, the fluid pressure at the fluid inlet forces tile ball to seat on the O-ring closest to the fluid outlet. In that position, the ball allows fluid flow through the valve. To prevent fluid backflow through tile valve, the ball seats on the O-ring closest to the fluid inlet.
Another valve with a backflow preventer is disclosed in U.S. Pat. No. 4,287,905 to Iglesias. That valve, which is for a water faucet, incorporates a check valve to prevent water backflow. The check valve is provided in the form of a hinged flap disposed in the main flow channel. The flap is provided with a gasket that is positioned next to a fluid opening near the fluid inlet. To prevent fluid backflow through the valve, the hinged flap moves so that the gasket is forced against the fluid opening, thus sealing the opening.
One disadvantage of the valves disclosed in the Brimley, et al. and Iglesias patents is that the means for preventing fluid backflow is provided in the main flow channel of the valve, thus obstructing the fluid flow through the valve during normal operation.